Fracturing oil bearing formations



,mations containing the same.

2,798,551 morirme on. animato ronMafrioNs;

n Ben W. Sewell, Tulsa, Okla., assignor to Esso Research and Engineering Company, a corporation of Delaware.

Applicaties May 16, 1952, serial No; ass-,09s

' 2' claims. (cl. '16s- 42) I This invention relates' to a method and apparatus for increasing the productivity of oil from subterranean for- More specifically it re-v lates to the fracturing of formations,` in the vicinity of a bore hole or producing well to thereby facilitate the release of oil into tlie well.`

The rate at which a givenreservoir can produce oil intoa well boreis controlled to a large extent by the permeability of the formation and the pressure in the reservoir. Logs and coresfrorn a newly discovered-held may indicate a large oil accumulation, but if the permea- It is an object of the present invention to provide a 'method. and 'apparatusfor fractnng a formation Without the attendant loss of a'newith thislinvention an elastic sleeve surrounded by 'a woven metal sheath is placed in the bore hole and `hydraulic pressure' is applied within the rubber tube.

This expands steunt: in the borehole and frac-'mesme 1 formation. ln a 'preferred embodiment'of the invention vtheunit is made sufficiently smaller than the bore hole A1o to denean annulus into which is placed granular or massive packing material which will serve as a pressure transfer medium, thus obviating the use of the woven metal sheath. In this -embodiment, granular packing material, when of the proper size, will tend to be forced into the fractures formed and prevent thelatter from i" closing when pressure is released.

The nature and objects of the. invention will be more "readily appreciated when consideration is taken of the disclosures in the accompanying ldrawing, in which:

Fig. l is a schematic diagram showing one embodimentV "vof the invention in place in a bore hole, together with Vsurface .equipment to supply pressure tothe hydraulic i bility is too low, the reservoir may not be a commercial orte.` In other instancesja well in a formation having.`

moderately low permeability4 may be completed as. a good producer, but after the well has produced' for some time the pressure near the well bore may decline until production at a commercial rate is no longer possible. When either of these two conditions is encountered,

a means of stimulating the production of the well must be found or else'v it will have to be abandoned. Most stimulating techniques are designed to increase the permeability in that p art of nea'r the well bore.

It has long bcenrecognizcd that the productivity of an oil bearing formation can ybe increased by creating artificial fractures adjacent the producing well. This has been accomplished in the past by the use of explosives and mitted throughfa' viscous liquid such as hydrocarbon oil gel which is pumped into the producingv well in suicint volume and under; suliicient pressure to rupture the for-` mation. These gels are prepared by mixing a napalm soap (mixture ofalurninum soaps ofnaphthenic, oleic and I palmitic acids) with kerosene or crude eiland aft-er a gel of suiiicient' viscosity has been produced coarse sand is added to themigtture. The' gel and "sand'mixture is pumped down 'the well and into the productive formation` at high pressure' until a fracture of the formation results, which is usually indicated by a momentary drop in pump pressure. The gel then carries th'e sand into the fracture and when the gel is later broken down by a suitable degelling material it hows out of theV fracturel and leaves the sand in place to prop open the articiallyformed fractures or liow.l channels.' A

This method of creating artificial fractures has several disadvantages; Since all o il or gas producing formations must have some permeability, the viscous uid used is lost, to varying degrees, into. the formation whenl pressurev is applied'. Therefore, the yuid 4rn-ust be pumped at a sufficiently high rate to exceed this loss and buildup the relatively high pressure required for fracture. Not

the producing formation'which il,

more recently by the application of high pressures trans- Y the formation;

rupturingtube o r sleeve; v

Fig. 2 is a f ragmental sectional view taken II.II of Figure l; A

Fig. 3 is an `elevational view, partly in section, of auf embodiment of 'the invention utilizing the weight of the drill pipe to force uid within the elastic tube to rupture Fig. 4 is anenlarged sectional detailof a portion of Fig.'3 showing means for fixing the tube or sleeve to the.

mandrel; Fig. Sis anenlar'ged sectional detail similar to Fig. 4

and showing means for slidably holding theilower end. of the sleeve on the mandrel;-

Fig. 6 isa rotated sectional view on line ing thev sleeve on the mandrel;

Fig.l l is an elevational view partlyin section show ing Ian embodiment of theinvention utilizing a precharged gas chamber for applying pressure within the elastic sleeve; v

Fig. 8 is an elevational view in section showing an eme bodiment utilizing a reversible electric motor and a fluid chamber for applying I pressure withinthe elastic tube; and

Fig. 9 'is an elevational sectional view s hoivingan em;

bodiment in which the rup'turing sleeve is surrounded with granular ll material in the bore hole.

Referring now specifically to Fig. 1 one form of ap paratus is shown in position in a bore hole 11,the apparatus comprising an elasticv sleeve-or hollow'tube 12 surrounded by a woven metal'sheath 13, the sleeve and sheath being fastened to a' supporting member 1 .4 which in turn is attached to pipe 15 which :extends through the 5 bore hole to the surface. Fluid is pumped through pipe 15 into the sleeve by means of a'pump 16'. The pressure 'of thej fluid can be followed by means of gage 20 and when the pressure is to be released valve 19`rnay be' opened. Valve 18 may be employed to hold the pressure only doesthis require ka lot of heavy surface equipment butthere is .danger of -damaging the'forxnations, withrespect to oil productivity, by the fluid that is forced into.

the pores of the formation. The method has the further disadvantage that 'once' a fracture occurs tlluid loss beplished.

'In'l comes so great that further rupturing lcannot be accomjbuilt up by the pump 'and a check valve. In Fig. 2, which is a fragmentary sectional view taken on line II-1I of Fig. l, is shown the result obtained byA exertingpressure on' the walls 4ofthe bore' hole, a nunk. 'ber 'of fractures 22 being formed through which increased production of oil may b e obtained.

Instead of supplying pressure from the surface, 'it il l also possible to employ the weight of the drill pipe tov furnish the desired pressure for expaudingihe sleeve against the walls of the bore hole. One suitable apparatus f 2,798,551 A-P-atex'tted' July 9, 1957 y y duid and without dang'erfof: impainng the productivity of the formation. Inaceord-` on line'- VI- VI of Fig. 4 showing a p ortion of the split ring used for holdmay advantageously comprise 'ff f ortliis purpose ,is shown in sectional through cable 70 which also supports the body within the thatterminates ina lower'inose portion 25.. Mandrel 23 has an inner chamber24 within whichfa piston 28 is ,slidably fitted, the piston being connected to a tube or rod -29 Whichin turnmaybe connected toa drill pipe .or drill collar; Thus when the apparatusis fastened to adrill pipe and set onthe bottom of the bore hole the.

weight of the drill pipe may be exerted to drive' piston 28 downward to force liquid from' chamber 2 4 into sleeve 12'through ports 31 and thus expand the sleeve against the bore hole walls to fracture the formation in the same manner as with the embodiment of Fig. 1. A shear pin 30 maybe used to prevent motion of the piston 28 until the bottom ofthe b ore hole is reached. Sleeve 12 is fastened to mandrel 23 by means of rings 26 and 27.'

Preferably ring27 is arranged for slidable movement along mandrel 23 to compensate for-the slight shorteningv the sleeve in fluid form, and permitted to set up beforel borehole.

As mentionedpreviously, it is preferred that the rup-' ture unit b e made sufcientlysmaller thanthe borehole to define an annulus into which granular or massive packingmatenal or -ll is placed so that this material may `serve as a pressure transfer medium furthe fracture sleeve. This enables greater pressures tobe applied to the formation without rupturing thefracture sleeve. @ne Y form of apparatus that'may be employed4 for this lemn bc-diment of the invention 'is shown in-Fig. 9, the tube or sleeve 62 being supported on body 61 and the apparatus forming with the bore hole an nautilus-'68 into which granular material such, as sand, tine gravel, small metal pellets orthe like maybe' placed.v Alternatively, massive till materialy may be used, such as cement orplastic, such material being introduced into the bore hole around the pressure is applied. Still- Aar'ioth'er alternative is t'o 5 employ a combination-of granular. material around the sleeve anda cap .of cement abovethc granular material y to confine the latter for more effective pressure transfer.

wardly facing teeth 35 in to which'the fabric-reinforced elastic sleeve 12 is pressed by means of split ring v 26. The arrangement in Fig. 5 is similar except that asliding seal spacer 33 is provided which may slide along mandrel 23, one or more 0-r'ing seals 34 being provided in suitable .grooves in. spacer 33 to prevent leakage of uid past the spacer.

As shown 1n Fig. 6 sufficient pressure to hold sleeve 1,2 in place is lr' btain ed by means of the split rings 26 which may be tightened by means of bolts 37.' e

Instead-of hydraulicpressure, gas pressure may also bev employed for expanding the fracture tube' or sleeve. One

' embodiment of this phase of the invention is shown in Fig. 7. The sleeve 12 is fastened to a cylinder 44 bymeans of split rings 26 and 27'in the same manner a's-in Fig. 3- and the cylinder is supported `in the bore hole byv K a cabley 41. Cylinder 4U. has an inner pressure chamber `45 containing a gas under pressure, the gas being held within the chamber by means of a rupture disc 48. When vit i's desired'to release gas from the chamber to inate the tube the rupture disc is broken by means of a plunger 52` arranged within plunger chamber 46 and held in place by plug 53. Thus after the apparatus is lon. ed f vto the bore hole on cable 41 a bumpersleeve 42 sur rounding cable 41 may be' dropped down the'bore hole .to strike the top of plunger 52 and drive it against disc 4 8, thereby rupturing the same and permitting gas to escape from chamber 45 through conduit 4 7 into chamber 46 and thence'into intlation tube 51 which terminates tube-12.

' When itis desired to4 deflate the fracture sleevethis l may be done by exerting a sharp pull on cable 41 which. will cause rod 55- to rupture detiation dist- 56, permitting the gasto escape into,4 ination chamber4 57 and out through port 59. The upward travelof rod 55 and cable With the fill-material in place, the sleeve is expanded..` f v,

by. forcing duid from chamber 64 through conduit 65 and ports 66 into annular space 63. The'prcssure will be transferred through-the lill material to the ivalls 'of the bore hole to rupturethe formation in the .same mannermmiw'Y tool to enable its removal, after which the cement may be drilled out. When granular 'material such as sand is used some of the' granular material Will-be forced into the fractures thatare produced. It is to be understood that any of the other structural embodiments of the invention may also be employed with the granular or massive fill material in the manner shown in Fig. 9.

The scope of this invention is to be limitedonly by the appended claims and is not Confined to the'particular embodiments hereindescribed by way-of'cxarnple.

What is claimed is: .1. A method of fracturing a subterranean oil-bearing formation frcma wel-l bore penetrating the formation so as to improve its oil productivity, which comprises placing an expansible holiow elastic tube in the well bore adjacent the formation'n a manner defining an annulusy between the tube a-nd the formation, filling said annulus with granular packing material, exerting sutiicient vtluid pressure within said tubc to forcesaid packing 'material against said formation and to fracture the formation in the vicinity ,of the well bore, continuing the exertion of uid pressure within the elastic tube to `force at least in ports 50 which communicate .with the interior of being supported on the body 7 1 by the'seal arrangement shown in Fi-g's. 4 and 5. When the pressure is to beA released the motor is 'reversed' and the iuid is pumped back into the sump. Current for the motor is suppliedv aportion of the packing'material into theresulting fractures, thereafter releasing the' fluid pressure on the, elastic tube;.

i Y2. 'A method as defined in 'claim 1 in which the granu- .lar packing material is sand,

References Cited in the le of this'patent UNITED STATES PATEN'IS Doyle May .27, 1902 

1. A METHOD OF FRACTURING A SUBTERRANEAN OIL-BEARING FORMATION FROM A WELL BORE PENETRATING THE FORMATION SO AS TO IMPROVE ITS OIL PRODUCTIVITY, WHICH COMPRISES PLACING AN EXPANSIBLE HOLLOW ELASTIC TUBE IN THE WELL BORE ADJACENT THE FORMATION IN A MATTER DEFINING AN ANNULUS BETWEEN THE TUBE AND THE FORMATION, FILLING SAID ANNULUS WITH GRANULAR PACKING MATERIAL, EXERTING SUFFICIENT FLUID PRESSURE WITHIN SAID TUBE TO FORCE SAID PACKING MATERIAL AGAINST SAID FORMATION AND TO FRACTURE THE FORMATION IN THE VICINITY OF THE WELL BORE, CONTINUING THE EXERTION OF FLUID PRESSURE WITHIN THE ELASTIC TUBE TO FORCE AT LEAST A PORTION OF THE PACKING MATERIAL INTO THE RESULTING FRAC- 